Insulated electrical conductor



.l 1 .1 U umnuu May 25, 1948. w. McMAHON 2,442,307

INSULATED ELECTRI CAL CONDUCTOR Filed Aug. 30, 1944 FINISHING COATINGC'OTTON ERA/D IMPREGNATED COMPRISING STEAR/NE P/T'CH WITH AFP L CJATURANT CONTAIN/N6 ZINC PENTACHLOROPHENATE COTTON BRA/D IMPREGNATEDWITH ASPHALT/C SATURANT FINISHING COATING COMPRISING STEAR/NE PITCH ANDCONTAINING ZINC PENTACHLOROPHENATE F u 3m 50, 77 COTTON BRA/DIMPREGNATED couPn/smc srunuv: P/TCHAND ASPHALT/C JATURANT CONT G 1 1PENTCHLOROPHKNAT'E CONTAINING ZINC PENTACHLOROPHENATE LEAD SHEA THINJULA TI ON INSULA TED WIRES E COVERING IMPREGNATED WITH ASPHALT/CJATUHANT CONTAINING ZINC PENTACHLOROPHENATE IN VEN TOR W. MC MAHON erATTORNEY V TWA-1" All. in A ah-- Patented May 25, 1948 UNITED STATESPATENT OFFICE INSULATED ELECTRICAL CONDUCTOR Application August 30,1944, Serial No. 551,826

7 Claims.

This invention relates to fibrous materials such as cellulosic materialsnormally subject to deterioration or decay due to fungal or bacterialaction, which are impregnated and/or coated with a material containingan agent which inhibits fungal or bacterial action. More particularly,the present invention relates to electrical conductors having insulatingor protective jackets comprising such impregnated or coated fibrousmaterials.

For convenience the present invention will be discussed in connectionwith electrical conductors each having a fibrous cellulosic jacket whichis impregnated or coated with a protective compound containing an agentwhich protects the jacket from fungal or bacterial action which cancause decay or deterioration.

Electrical conductors, such as telephone drop wires or the like, formany uses are provided with an outer jacket of fibrous cellulosicmaterial designed to protect the inner structure of the conductor, whichusually contains insulat ing material, against deterioration fromabrasion, weathering, oxidation, moisture, or other causes. Thecellulosic jacket, which usually takes the form of a braided or knittedcovering of cotton or other cellulosic thread, is impregnated and/orcoated with a suitable compound to protect the jacket as well as theinner insulating material against deterioration due to causes such asthose indicated above.

Protective compounds comprising asphalts such as petroleum asphalts,and/or pitches such as stearine pitches or coal tar pitches, usually areemployed. These protective compounds are usually applied to thecellulosic material while the compounds are molten and hence atconsiderably elevated temperatures; the use of solvents is generallyavoided because of the economic loss involved if they are wasted andbecause of the difficulties involved in recovering them. Thetemperatures at which the protective compounds are applied are usuallyquite high to cause the viscosity of the protective compounds to be solow as to permit thorough impregnation or covering.

It has been found, however, that when electrical conductors havingjackets of fibrous cellulosic material thus impregnated or coated withsuch protective compounds are employed in environments where they are inclose proximity to or contact with the earth, the cellulosic materialsof the jackets often deteriorate or decay apparently because of fungalor bacterial action. It has been also found that when such conduc torsare employed in environments in which they are remote from the earth, aswhen they are strung between poles or in buildings, the cellulosicmaterials of the jackets often deteriorate or decay apparently becauseof fungal action, particularly if the conductors are disposed in warm,damp places. The deterioration or decay occurs even though the fibrouscellulose jacket is impregnated or coated with a protective compound,such as one comprising asphalt or stearine pitch, which would beexpected to protect the cellulosic material against fungal or bacterialattack.

Destruction or deterioration of the protective cellulosic jacket exposesthe inner structure of the conductor to deterioration due to abrasion,oxidation, moisture, weathering, or other causes and renders theconductor dangerous or inoperative.

It is desirable to incorporate in the impregnated cellulosic materialone or more substances having pronounced fungicidal and bactericidalproperties to protect the cellulosic material. In general, such asubstance should have the following properties:

It should, of course, be effective to inhibit or prevent the life andgrowth of those fungal and/ or bacterial organisms which attack thecellulosic material of the jacket.

It should have a sufficiently powerful biocidal effect and be ofsufficiently low cost to permit its economical use.

It should be miscible and compatible with the impregnating or coatingcompound so that it will remain in the compound during the applicationof the compound to the cellulosic jacket and will not appreciably belost during use of the conductor by blooming or exudation from thesurface.

The substance should be resistant to heat so that it does not break downinto useless or harmful substances under the elevated temperaturesemployed in impregnating or coating of the cellulosic jacket.

The substance should have a low vapor pressure, so that harmful amountsof it are not lost due to evaporation during the high temperatureapplication of the protective compound, or during use of the electricalconductor.

The substance should have a low solubility in water so that it will notleach out of the conductor during use and so that water solutions of thesubstance cannot permeate or attack rubber which may be employed in theinternal structure of the conductor.

The substance should not appreciably ionize in water since ionizationwhich might occur because of moisture encountered during use of theconductor might impair the insulation resistance of the insulatedelectrical conductor.

The substance of itself should not decrease the electrical insulationproperties of the electrical conductor, or increase its inflammability.

The present invention provides an electrical conductor having animpregnated or coated fibrous cellulosic jacket containing zincpentachlorophenate, which salt greatly inhibits or entirely preventsdeterioration and decay of the cellulosic material and whichsubstantially if not who y satisfies all the requirements indicated HUUMabove for a satisfactory inhibitor of fungal or bacterial action whichcauses deterioration or decay.

These and other advantages of the present invention, and the structureof electrical conductors embodying the invention will be more fullyapparent from the following description in connection with the appendeddrawings, in which:

Fig. 1 represents to an enlarged scale a por tion of an electricalconductor having an outer protective fibrous cellulosic jacketimpregnated with a protective compound containing zincpentachlorophenate;

Fig. 2 represents to an enlarged scale a portion of an electricalconductor having an outer protective fibrous cellulosic jacket coatedwith a protective compound containing zinc pentachlorophenate;

Fig. 3 represents to an enlarged scale a portion of an electricalconductor having an outer protective fibrous cellulosic jacketimpregnated with a protective compound containing zincpentachlorophenate and coated with a protective compound containing zincpentachlorophenate; and

Fig. 4 represents to a smaller scale a portion of an electricalconductor of the cable type adapted to be buried in the earth andcomprising a metallic sheath covered with an outer protective fibrouscellulosic jacket impregnated with a protective compound containing zincpentachlorophenate.

Zinc pentachlorophenate is a white crystalline solid which issubstantially insoluble in water but soluble in certain organicsolvents. It may be produced by mixing a water solution of a zinc saltsuch as zinc chloride or zinc sulphate with a water solution of sodiumpentachlorophenate or other water soluble pentachlorophenate. Thequantities of zinc salt and pentachlorophenate should be chemicallyequivalent. The precipitate resulting from the reaction of these twocompounds is zinc pentachlorophenate. It may be filtered, washed anddried and is then ready for use. When produced on a commercial scale itmay contain small amounts of chlorinated phenols and other saltsthereof.

The protective compounds in connection with which the zincpentachlorophenate are employed are those which must be heated torelatively high temperatures of about 100 C. or more in order to permittheir application in the molten state at a sufiiciently low viscosity tothe fibrous cellulosic material; zinc pentachlorophenate has the unusualproperty of resisting heat so well that it does not break down intoharmful compounds, such as those including hydrochloric acid or thelike, as do other chlorinated phenolic compounds, even though it issubjected to temperatures from about 100 C. to as high as about 160 C.The protective compound advantageously comprises petroleum asphalt,stearine pitch, coal tar pitch or mixtures thereof, hereinafter forconvenience termed hydrocarbon protective compounds. It advantageouslyis of the type customarily employed for impregnation or coating offibrous cellulosic jackets on electrical conductors, but the protectivecompound may be formed of or include other materials such as syntheticresins. These asph'altic stearine pitch or coal tar compounds in generalrequire application temperatures of above about 100 C. to permitsatisfactory impregnation or coating.

According to one process embodying the in vention, the zincpentachlorophenate is disso ed in the molten protective compound priorto its application to the cellulosic jacket of the electrical conductor,in an amount ranging from about one to ten per cent or more by weight ofthe protective compound; from two to four per cent of zincpentachlorophenate by weight of the protective compound is advantageousfrom a fungicidal and bactericidal standpoint as well as from aneconomical standpoint. After the salt has been dissolved in theprotective compound, the molten protective compound is impregnated intoor coated onto the cellulosic jacket on the conductor in any suitableknown manner.

According to another process embodying the invention, the zincpentachlorophenate may be applied to the fibrous material of the jacketbe fore it is impregnated or coated with the protective compound, andthe protective compound then applied. For example, the fibrouscellulosic material, either before or after being formed into the jacketon the conductor, may be treated with a volatile liquid having dissolvedtherein the salt; after evaporation of the liquid and deposition of thesalt on the fibres, the cellulosic material may be impregnated or coatedwith the protective compound which may be in the molten state and at theelevated temperature indicated above.

A third process embodying the invention comprises first treating fibrouscellulosic material with a suitable solution of a zinc salt and thenwith a suitable solution of an pentachlorophenate, or vice-versa, toprecipitate zinc pentachlorophenate upon the fibres of the cellulosicmaterial. A jacket comprising such fibrous material containing zincpentachlorophenate and formed about an electrical conductor is thenimpregnated or coated with a molten protective compound. At least aportion of the zinc pentachlorophenate dissolves in the protectivecompound.

The insulated electrical conductor shown in Fig. 1 comprises a metalcore I, such as a copper wire, surrounded by a layer 2 of a rubbercompound. This layer 2 is surrounded by a cellulosic jacket 3 shown as acotton braid. The jacket 3 is impregnated with a hydrocarbon protectivecombound 4 essentially comprising asphalt derived from crude oil andcontaining between about 10 and about 25 per cent by weight of a highmelting wax such as montan wax which serves to reduce the viscosity ofthe asphalt; this compound contains between about 2 and about 4 per centof zinc pentachlorophenate by weight of the sat urant. The compound maybe applied to the cellulosic jacket by any of the known procedures whilemolten and at a temperature of over 100 C.; the zinc pentachlorophenateis dissolved in the saturant while it is molten and before applicationof the saturant. The impregnated cellulosic jacket 3 is covered with acoating 5 of a finishing hydrocarbon protective compound comprisingbetween about '70 per cent and about per cent of stearine pitch derivedfrom cottonseed, from about 0 per cent to about 20 per cent of asphaltderived from crude oil, and a minimum of about 10 per cent of highmelting wax such as montan wax. The finishing compound is applied in amolten state at a temperature of over C. by any one of the usualprocedures. The conductor may be coated with one or more materials whichreduce abrasion and serve as a lubricant; thus, the conductor may becoated with flake mica.

In the insulated electrical conductor shown in Fig. 2, the metal core 6which is a copper wire is also surrounded by a layer 1 of a rubber com-Pound. This layer 1 is covered by a cellulosic jacket 8 comprising acotton braid which is impregnated while molten and at a temperature ofover 100 C. with an asphaltic saturant 9 similar to that described aboveas being employed in the embodiment of Fig. 1, but not containing anyzinc pentachlorophenate. A finishing compound which is applied whilemolten and at a temperature of over 100 C. over the impregnated cottonbraid to form a layer ID has dissolved therein from about 2 to about 4per cent of zinc pentachlorophenate; this finishing compound comprisesin addition to the zinc pentachlorophenate from about 70 per cent toabout 90 per cent of stearine pitch, from about 0 per cent to about 20per cent of asphalt derived from crude oil, and a minimum of 10 per centof high melting wax. The surface of the finished conductor may be coatedwith one or more materials to reduce abrasion and increase lubrication.

In the conductor shown in Fig. 3, both the saturant and the finishingcompound contain zinc pentachlorophenate. More specifically, theinsulated conductor comprises two metal cores H. each surrounded by aninsulating layer 12 of rubber compound. Both of the insulated cores areenclosed in a braided cotton jacket I3 which is impregnated with asaturant I4 containing zinc pentachlorophenate and identical with thatdescribed above in connection with the conductor ;of Fig. 1. Theimpregnated braided jacket has a coating ll: of a finishing compound ofthe type described above in connection with the conductor of Fig. 2 andcontaining zinc penta-chlorophenate.

In the electrical conductor of Fig. 4, the zinc pentachlorophenate isdissolved in the saturant which impregnates a cellulosic jacketsurrounding a metal sheath. More specifically, the electrical conductorof Fig. 4 comprises a multiconductor lead-covered cable of the typeadapted to be buried in the earth and comprising a plurality of metalconductors 16, each surrounded by an insulating layer ll of paper or thelike, all being enclosed in an insulating jacket I 8 formed of suitablematerial such as rubber, paper, or the like, and serving to separate theconductors from the surrounding tubular lead sheath I9. The lead sheathI9 is covered by a jacket formed of wrapped jute impregnated with anasphaltic or coal tar saturant containing between about 2 and about 4per cent by weight of zinc pent-achlorophenate. The saturant, which maybe the kind described above in connection with the embodiment of Fig. l,is applied to the jute jacket while it is in the molten condition and ata temperature of 100 C. or over.

It is the usual practice to enclose a lead-covered cable which is to beburied in the earth with a jute or other cellulosic jacket impregnatedwith a suitable hydrocarbon saturant, since it has been found that thecellulosic jacket protects the lead sheath of the cable against damagedue to abrasion during the operation of burying the cable :and duringthe settling of the cable in its trench after it has been buried. Formaximum protection of the cable, it is desirable that the cellulosiccovering endure throughout the period during which settling occurs,which may be several months. When the saturant contains a suitableamount of zinc pentachlorophenate, the cellulosic protective jacket forthe lead sheath is preserved from rotting for a period of many monthsand throughout the period during which settling occurs. Consequently,the life of buried cables is considerably increased.

In the above indicated embodiments various other modifications may bemade. For example, the layer of insulation shown in each of Figs. 1, 2and 3 as surrounding and contacting the metal core, and which isdescribed as being formed of a rubber compound, may also be formed ofsynthetic rubber, synthetic resin, or other suitable insulatingmaterial. The impregnated jacket which is described as being a cottonbraid may also be a cotton wrapping, a wrapping of braid, a feltedcellulosic fibrous covering, or may be any other material which issubject to deterioration by bacterial or fungal action. The saturant andfinishing compounds may be formed of other materials or of othercompositions than those indicated above; those described areadvantageous because of their low cost, effectiveness, and ease ofapplication. In the embodiment of Fig. 4, various other modificationsmay be made also. For example, other types of cellulosic jackets thanthe wrapped jute covering described therein may be employed, and othertypes of saturants than the asphaltic saturant mentioned may be used.

The insulated conductor structures shown in the drawings are merelyillustrative of the invention and it is apparent that other conductorstructures embodying zinc pentachlorophenate may be made and may beemployed. Various modifications other than those indicated above may bemade in the structures embodying the invention, and in the process ofincorporating zinc pentachlorophenate in the structures embodying theinvention.

Electrical conductors having jackets formed of cellulosic othermaterials subject to attack and deterioration due to fungal and/orbacterial action and which jackets are saturated or coated with highmelting materials containing zinc pentachlorophenate, are veryadvantageous because they do not deteriorate even though employed inenvironments where they are exposed to bacterial or fungal organismswhich would tend to attack the jackets. The zinc pentachlorophenate ishighly effective in inhibiting or preventing the life and growth offungal or bacterial organisms which would otherwise harm the jacket. Ithas a powerful biocidal effect so that small proportions of it may beemployed, and its cost is sufliciently low to permit its economical use.It is miscible and compatible with the impregnating or coating compoundsusually employed in the manufacture of electrical conductors, so that itremains in such compounds during application of the molten compound tothe jacket and does not bloom or exude from the surface of a compoundduring use of the conductor. The zinc pentachlorophenate is resistant toheat so it does not break down into useless or harmful substances evenunder the elevated temperatures employed in impregnating or coating thejacket. It has a high vapor pressure so that harmful amounts are notlost due to evaporation during the high temperature application of theimpregnating or coating compound or during use of the electricalconductor. It has a low solubility in water and hence does not leach outof the conductor during use and does not form water solutions which canpermeate or attack the rubber. The substance does not appreciably ionizein water and hence cannot form ionized conducting solutions which canpermeate the insulation material and cause a decrease in insulationresistance, as can occur if alkali or alkaline earth salts are employed.The zinc pentachlorophenate 'does not harmfully decrease the electricalinsulation properties of the electrical conductor and does not decreaseits resistance to flame; in fact, the salt has flame-proofing propertiesbecause of its chlorinated hydrocarbon structure. Other advantages areapparent to those skilled in the art.

It is intended that the patent shall cover by suitable expression in theappended claims whatever features are of patentable novelty residing inthe invention.

What is claimed is:

1. An electrical conductor comprising a conducting core and a jacketsurrounding the core formed of a non-metallic material susceptible tobacterial or fungal attack, which jacket has associated therewith aprotective compound which because of its temperature-viscosityrelationship must be heated to a temperature of at least 100 C. duringits application to said jacket, said pro-- tective compound containing abiocidal agent which is compatible with said protective agent, and whichdoes not decompose substantially at temperatures up to 160 C., saidbiocidal agent being zinc pentachlorophenate.

2. An electrical conductor comprising an insulated conducting core and,surrounding said core, a cellulosic jacket coated with a hydrocarboncompound which because of its temperatureviscosity relationship must beheated to a temperature of at least 100 C. during its application tosaid jacket, said hydrocarbon compound containing a biocidal agent whichis compatible with said hydrocarbon compound, which is not substantiallysoluble or ionizable in water, which does not decompose substantially attemperatures up to 160 C. and which does not substantially increase theflammability or substantially decrease the insulating value of thehydrocarbon compound, said biocidal agent being zinc pentachlorophenate.

3. An electrical conductor comprising a conducting core, insulatingmaterial surrounding said core, and a cellulosic jacket surrounding saidinsulating material which jacket is impregnated with an asphalticimpregnating compound which because of its temperature-viscosityrelationship must be heated to a temperature of at least 100 C. duringits application to said jacket, said asphaltic impregnating compoundhaving dissolved therein between about 1 and about 10 per cent by weightof a biocidal agent which is compatible with said asphaltic impregnatingcompound, which is not substantially soluble or ionizable in water,which does not decompose substantially at temperatures up to 160 0., andwhich does not substantially increase the flammability or substantiallydecrease the insulating value of said asphaltic impregnating compound,said biocidal agent being zinc pentachlorophenate.

4. An electrical conductor comprising a conducting core, insulatingmaterial surrounding said conducting core, a cellulosic jacketsurrounding said insulating material which jacket is impregnated with aprotective compound, and a coating on said jacket of a finishingcompound which must be heated to a temperature of at least 100 C. whileit is being applied as a coating to said cellulosic jacket comprisingstearine pitch and having dissolved therein between about 1 and about 10per cent by weight of a biocidal agent which is compatible with saidfinishing compound, which is not substantially soluble or ionizable inwater, which does not decompose substantially at temperatures up to 160C., and which does not substantially increase the flammability orsubstantially decrease the insulating value of said finishing compound,said biocidal agent being zinc pentachlorophenate.

5. An electrical conductor comprising a plural ity of insulatedconducting cores, a metal sheath surrounding said insulated cores, and acellulosic jacket surrounding said metal sheath which jacket isimpregnated with a protective compound which because of itstemperature-viscosity relationship, must be heated to a temperature ofat least C. during its application to said jacket, said protectivecompound containing a biocidal agent which is compatible with saidprotective agent, which is not substantially soluble or ionizable inwater, which does not decompose substantially at temperatures up to C.and which does not substantially increase the flammability orsubstantially decrease the insulating value of the protective compound,said biocidal agent being zinc pentachlorophenate.

6. An electrical conductor comprising a conducting core and a jacketsurrounding the core formed of a fibrous cellulosic material having uponits fibres a biocidal agent which is not substantially soluble orionizable in water which does not decompose substantially attemperatures up to 160 C., and which does not substantially increase theflammability or substantially decrease the insulating value of saidcellulosic material, said biocidal agent being zinc pentachlorophenate,which jacket has associated therewith a protective compound depositedfrom the molten condition said protective compound being one which mustbe heated to a temperature of at least 100 C. during its application tosaid celluloslc jacket.

'7. A process of protecting the cellulosic jacket of an electricalconductor comprising a conducting core surrounded by a cellulosicjacket, which process comprises applying to said cellulosic jacket at atemperature of at least 100 C. a molten protective compound havingdissolved therein at least about 1 per cent of a biocidal agent which iscompatible with said protective agent, which is not substantiallysoluble or ionizable in Water, which does not decompose substantially attemperatures up to 160 C. and which does not substantially increase theflammability or substantially decrease the insulating value of theprotective compound, said biocidal agent being zinc pentachlorophenate.

WILLIAM McMAHON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,732,984 Packer Oct. 22, 19291,863,147 Young June 14, 1932 2,209,970 Hay Aug. 6, 1940 2,320,201Szilard May 25, 1943 OTHER REFERENCES Chemical Abstracts for 1942,column 5329; article by Scott with reference to 5% sodium pentachlorophenolate in No. 1 fuel oil and called Santobrite. (Copy of publicationin Div. 6, U. S. Patent Office.)

